REFLECTOR:Brake problem.

Ronnie Brown reflector@tvbf.org
Sat, 4 Oct 2003 07:43:58 -0400


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The caliper needs to be vertical - not horizontal, i.e. the bleeder =
valve down and the brake line at the top.  The problem here is that the =
three pucks are interconnected, each gets its fluid from the adjacent =
puck.  If you will draw a 10" circle, then draw three 3" circles, with =
their circumferences just touching and their centers on the =
circumference of the 10" circle.  Now hold the paper up, rotate the =
paper with the one of the 3" circles near the bottom, you will see that =
there is space at the bottom and even the middle circle that air could =
trap in the top of the circle.  This is what you are trying to remove =
when back bleeding the brakes.

As several have noted, you can tip the nose up and improve the situation =
- this is for a FIXED gear installation.  The retract models have the =
caliper on the rear of the mains.  I tried collapsing my nose gear and =
putting the nose on the ground to improve the orientation of the bottom =
caliper but that didn't fix it.

I can't recall who discovered this problem a year or two ago. It worked =
for me after having a soft brake after flying several of my test =
flights, then I had to start pumping my right side brake to get any =
brake action.  A new master cylinder did not fix the problem.  Then I =
removed the caliper and rebled the brakes with the caliper standing =
vertically.  That was 60 hours ago and they are still working perfectly.

Ronnie
  ----- Original Message -----=20
  From: PUSHERPILOT@wmconnect.com=20
  To: reflector@awpi.com=20
  Sent: Saturday, October 04, 2003 2:27 AM
  Subject: REFLECTOR:Nose gear sag and brake problem.


  One of the suggestions to bleed the brakes was to remove the caliper =
and move it while bleeding.  I had not installed my nose gear doors =
since painting and thought that bleeding the brake when up in the well =
might make a difference.  Fix the brake problem and reattach the nose =
gear doors, a two for one.=20

  Bleeding the brake with the caliper horizontal didn't help.  However, =
I now have a new problem, the nose gear is not retracting enough to =
close the doors.  The sag is about 1/2 " and the gear can be pulled up =
easily by hand.  I haven't changed anything since I last retracted the =
gear.  Brendan suggested that the pressure switch may be cutting off too =
soon.  I turned the hi pressure screws in 1 1/2 turns, 1/4 turn at a =
time with no change.  I also seem to recall that years ago when checking =
the system with a pressure gage, the adjustments didn't work.  Perhaps =
Al Gietzen found the same thing.  Does anyone have a suggestion?  I had =
planned to fly to Copper State, now Xmas is in doubt.=20

  Mel Bina  STD  RG=20

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<BODY bgColor=3D#ffffff>
<DIV><FONT size=3D2>The caliper needs to be vertical - not horizontal, =
i.e. the=20
bleeder valve down and the brake line at the top.&nbsp; The problem here =
is that=20
the three pucks are interconnected, each gets its fluid from the =
adjacent=20
puck.&nbsp; If you will draw a&nbsp;10" circle, then draw three 3" =
circles, with=20
their circumferences just touching and their centers on the =
circumference of=20
the&nbsp;10" circle.&nbsp; Now hold the paper up, rotate the paper with =
the one=20
of the 3" circles near the bottom, you will see that there is space at =
the=20
bottom and even the middle circle that air could trap in the top of the=20
circle.&nbsp; This is what you are trying to remove when back bleeding =
the=20
brakes.</FONT></DIV>
<DIV><FONT size=3D2></FONT>&nbsp;</DIV>
<DIV><FONT size=3D2>As several have noted, you can tip the nose up and =
improve the=20
situation - this is for a FIXED gear installation.&nbsp; The retract =
models have=20
the caliper on the rear of the mains.&nbsp; I tried collapsing my nose =
gear and=20
putting the nose on the ground to improve the orientation of the bottom =
caliper=20
but that didn't fix it.</FONT></DIV>
<DIV><FONT size=3D2></FONT>&nbsp;</DIV>
<DIV><FONT size=3D2>I can't recall who discovered this problem a year or =
two=20
ago.&nbsp;It worked for me after having a soft brake after =
flying&nbsp;several=20
of my test flights, then I had to start pumping my right side brake to =
get any=20
brake action.&nbsp; A new master cylinder did not fix the problem.&nbsp; =
Then I=20
removed the caliper and rebled the brakes with the caliper standing=20
vertically.&nbsp; That was 60 hours ago and they are still working=20
perfectly.</FONT></DIV>
<DIV><FONT size=3D2></FONT>&nbsp;</DIV>
<DIV><FONT size=3D2>Ronnie</FONT></DIV>
<BLOCKQUOTE=20
style=3D"PADDING-RIGHT: 0px; PADDING-LEFT: 5px; MARGIN-LEFT: 5px; =
BORDER-LEFT: #000000 2px solid; MARGIN-RIGHT: 0px">
  <DIV style=3D"FONT: 10pt arial">----- Original Message ----- </DIV>
  <DIV=20
  style=3D"BACKGROUND: #e4e4e4; FONT: 10pt arial; font-color: =
black"><B>From:</B>=20
  <A title=3DPUSHERPILOT@wmconnect.com=20
  =
href=3D"mailto:PUSHERPILOT@wmconnect.com">PUSHERPILOT@wmconnect.com</A> =
</DIV>
  <DIV style=3D"FONT: 10pt arial"><B>To:</B> <A =
title=3Dreflector@awpi.com=20
  href=3D"mailto:reflector@awpi.com">reflector@awpi.com</A> </DIV>
  <DIV style=3D"FONT: 10pt arial"><B>Sent:</B> Saturday, October 04, =
2003 2:27=20
  AM</DIV>
  <DIV style=3D"FONT: 10pt arial"><B>Subject:</B> REFLECTOR:Nose gear =
sag and=20
  brake problem.</DIV>
  <DIV><FONT size=3D2></FONT><FONT size=3D2></FONT><FONT=20
  size=3D2></FONT><BR></DIV><FONT face=3Darial,helvetica><FONT =
size=3D2>One of the=20
  suggestions to bleed the brakes was to remove the caliper and move it =
while=20
  bleeding. &nbsp;I had not installed my nose gear doors since painting =
and=20
  thought that bleeding the brake when up in the well might make a =
difference.=20
  &nbsp;Fix the brake problem and reattach the nose gear doors, a two =
for one.=20
  <BR><BR>Bleeding the brake with the caliper horizontal didn't help.=20
  &nbsp;However, I now have a new problem, the nose gear is not =
retracting=20
  enough to close the doors. &nbsp;The sag is about 1/2 " and the gear =
can be=20
  pulled up easily by hand. &nbsp;I haven't changed anything since I =
last=20
  retracted the gear. &nbsp;Brendan suggested that the pressure switch =
may be=20
  cutting off too soon. &nbsp;I turned the hi pressure screws in 1 1/2 =
turns,=20
  1/4 turn at a time with no change. &nbsp;I also seem to recall that =
years ago=20
  when checking the system with a pressure gage, the adjustments didn't =
work.=20
  &nbsp;Perhaps Al Gietzen found the same thing. &nbsp;Does anyone have =
a=20
  suggestion? &nbsp;I had planned to fly to Copper State, now Xmas is in =
doubt.=20
  <BR><BR>Mel Bina &nbsp;STD &nbsp;RG</FONT> =
</FONT></BLOCKQUOTE></BODY></HTML>

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